1. Field of the Invention
The present invention relates to a system for integrating broadcasting and communication technologies and, in particular, to a sending and receiving system which facilitate the implementation of processing broadcast signals within an optimal level of quality of services.
2. Description of the Related Art
In general, broadcasting is characterized as a one-way transmission for reception by a group of unspecified viewers. A service provider and a network provider are the same entity for the provision of such broadcasts. In the conventional broadcasting, all broadcast channels are transmitted to viewers so that the viewers can select their desired channels through a set-top box, for example. As such, in this broadcasting scheme, unnecessary channels are transmitted to the broadcast-receiving apparatus.
In contrast, a general communication service is characterized as a two-way transmission involving point-to-point transmission and reception of messages. Unlike the broadcasting technique, the service provider and the network provider are different.
The different characteristics and implementation of the respective technologies described above and others are listed in the following Table 1.
TABLE 1ClassificationBroadcastCommunicationReceiverMultiple ofSpecified personunspecified personsFeeNot chargedChargedDirectionOne-wayTwo-waytransmissiontransmissionContentsPublicPrivateService and networkSameDifferentproviders
Traditionally, broadcasts were provided through a broadcast network while communication was performed through a communication network. Nowadays, broadcasts can be provided through a communication network, and vice versa. Thus, different broadcast and communication networks have converged in the form of integrated networks, i.e., satellite broadcasting using a communication satellite, a cable-television (CATV) network, a telephony business using a CATV network, data or paging-signal transmission using a ground wave for broadcast, etc. In addition, there is a growing trend of convergence of services where a broadcast service and a communication service are merged. With the development of ever-growing multimedia techniques, a new service having intermediate characteristics between the conventional broadcast and communication services has been developed. For example, one exemplary new service having the intermediate characteristics includes a data-casting service, a video-conference service, a video-on-demand (VOD) service, etc. As a result, the conventional media can be used in newer ways, including telemarketing, fax advertisement, etc.
Therefore, there is a need for a system for combining the broadcast and communication technologies using a CATV network from an aspect of a broadcaster, and a system for combining the broadcast and communication technologies based on an Internet protocol (IP) using a very high-speed, digital-subscriber-line (VDSL) network, etc., from an aspect of a communication carrier.
FIG. 1 is an exemplary broadcast and communication-integration system using a conventional cable-television (CATV) network. As shown, the integration system includes an optical line terminal (OLT) 100 located between a user 300 and a service node, which receives a broadcast signal from a broadcaster and a communication signal from a communication carrier in order to provide the integrated broadcast and communication services, such as a digital-broadcast service, an analog-broadcast service, a voice-telephone service, a video service, a high-speed Internet service, etc., to the user 300. The functions of OLT 100 include electro-optically converting the received broadcast and communication signals, combining the converted broadcast and communication signals to form a single optical signal, and sending the combined optical signal. Further, an optical-network unit (ONU) 200 is provided at the user side for sending an optical signal from the OLT 100 to the user 300. To this end, an optical cable connected between the OLT 100 and the ONU 200 and a two-way hybrid-fiber coaxial (HFC) network connected between the ONU 200 and the user 300 are provided.
According to the configuration above, the broadcast and communication-integration system using the CATV network must optically transmit a sub-carrier analog signal so that data can be transmitted. To improve the efficiency of transmission, the system has adopted a complex modulation scheme such as 64-quadrature amplitude modulation (QAM).
Note that a user-connection network is configured in the form of a coaxial cable, and its transmission bandwidth is limited to approximately 900 MHz. As the broadcast typically transmits all broadcast channels to all subscribers, the bandwidth utilization is not optimal. Meanwhile, a communication-service field provides the Internet, video-on-demand (VOD), etc., using a cable modem; thus each subscriber is forced to share the limited bandwidth. Accordingly, there is a problem of inefficient usage of bandwidth as the number of subscribers increases.
FIG. 2 is an exemplary broadcast and communication-integration system based on an Internet protocol (IP) associated with a conventional communication carrier. As shown, the integration system based on the IP using an x digital-subscriber-line (xDSL) network includes an optical-line terminal (OLT) 100 located between a user 300 and a service node for receiving a broadcast signal from a broadcaster and a communication signal from a communication carrier so that services such as a digital-broadcast service, an analog-broadcast service, a voice-telephone service, a video service, a high-speed Internet service, etc., are available to the user 300. An optical cable is connected between the OLT 100 and the ONU 200, and a high-speed subscriber-line (VDSL) network made of a copper line is connected between the ONU 200 and the user 300.
The integration system based on the IP using the xDSL network is configured to transmit at a unit of a packet. Thus, the system is unable to provide the seamless broadcast. In particular, a time delay can occur since a process for linking the packets is needed. For this reason, it is difficult for the broadcast to be transmitted and processed in real time. Therefore, the IP-based integrated system is unable to meet the current demand for high quality of the broadcast service. In addition, as the xDSL uses a copper line as a transmission medium, the bandwidth is limited due to the copper line's physical characteristics.
Accordingly, there is a need for an improved integrated system capable of overcoming the above-described problems and which provides additional advantages.